Curving G-function plots and picking closure

G-function plot of a typical DFIT.

G-function plots are routinely used to interpret diagnostic fracture injection test (DFIT) transients. Ideally, a plot of pressure versus G and G*dP/dG versus G should form a straight line. However, the G*dP/dG curve is very often curving. A typical DFIT transient is shown below.

Demystifying the G-function

Derivative of pressure with respect to the G-function

Diagnostic fracture injection tests (DFITs) are commonly interpreted by plotting pressure versus a function of time called the G-function. The G-function seems rather arcane and is often misunderstood. However, it has […]

Diagnostic Fracture Injection Tests: The Basics

A typical pressure response during injection in a DFIT.

In a diagnostic fracture injection test (DFIT), a relatively small volume of fluid is injected into the subsurface, creating a hydraulic fracture. After the end of injection, the pressure in […]